DESCRIPTION: To reveal mechanisms involved in the early stages of melanoma development, Dr. Ronai has elucidated the mammalian response to UV-irradiation, being the major etiological agent in melanoma development. Through the characterization of a novel UV-response element (URE) he has identified a cyclic AMP response element-binding protein (CREB) in B16 mouse melanoma cells and an activating transcription factor 2 (ATF-2) in human melanoma cells. Expression of a dominant negative CREB or of dominant negative ATF-2 (ATF2dn in human melanoma cells (MeWo) resulted in poor resistance to irradiation, and diminished expression of high molecular weight melanoma-associated antigen. It is the working hypothesis that changes in a particular subset of UV-related transcription factors can override genomic alterations which dictate characteristic phenotypes of human melanoma. While present studies provide direct support for this hypothesis, future studies are aimed at delineating the mechanism(s) by which selective changes in the transcription factor ATF2 can alter phenotypes of melanoma cells. For that Dr. Ronai proposes to: 1. Identify proteins that form heterodimers with ATF-2 in order to mediate its activities in MeWo-AFT2dn melanoma cells; 2. Identify critical domains which confer AFT2dn activities; 3. Test the ability of ATF2dn to modulate melanoma growth and metastatic potential in vivo. 4. Identify mechanisms involved in ATF2dn ability to alter melanoma phenotypes. Through the use of UV-irradiated melanocytes, melanoma and MeWo-AFT2dn, he will determine the changes in genes known to be regulated by ATF2 and expected to participate in the UV-response. Cellular components that are found to be modulated in MeWo-AFT2dn cells will be further evaluated for their inherent ability to alter radiation resistance and metastatic potential.